docs: def _get_subparsers(self):
      """Recursively get subparsers."""
  
      subparsers = []
      for action in self._actions:
        if isinstance(action, argparse._SubParsersAction):
          for _, subparser in action.choices.items():
            subparsers.append(subparser)
  
      ret = subparsers
      for sp in subparsers:
        ret += sp._get_subparsers()
      return ret